1. Field of the Invention
The present invention relates to electronic stepping counters using resonant tunneling diodes, and in particular to stepping counters using the periodic hysteresis characteristic of a resonant tunneling diode connected in series with a resistance.
2. Discussion of the Background
Electronic stepping counters are widely used in the art, and have numerous and various applications. It has also been suggested that resonant tunneling diodes (RTDs) may be used in multi-level logic circuits. In Potter et al, 1990 International Symposium on Circuits and Systems (May, 1990), a multi-level logic circuit is disclosed having stable operating points defined by the intersection of a load line with the folding characteristic of the RTD. However, defining the stable operating points in this manner allows only a limited number of points to be defined and requires rather large resistances to define a larger number of operating points, which is a great disadvantage in attempting to miniaturize the multi-level logic circuit and to obtain high speed operation.
Tan et al, Electronic Engineering, pp. 624-629 (October, 1967) connect a number of tunnel diodes in series to form a chain and bias the chain with a constant current source to produce a number of stable states in the positive resistance regions of the tunnel-diode chain output characteristic. Tan et al form a decade-scaler using the tunnel-diode chain. The circuit of Tan et al requires that the fall time of the voltage pulse be increased to avoid erroneous resetting of the circuit during the trailing edge transition of the input pulse, which severely limits the operating speed of the circuit. Thus, it is not possible to build high speed stepping counters using the circuit of Tan et al.